his effect activated at standby phase. while you summon him, you are already at your main phase.
this card only good if you need to recycle poly, but i prefer fusion recycling plant because it can return monsters too.

Oh my magical slime... this one is nasty. First off you'll only need one poly and still have its maximum potential available, you get a 2000def beast. Free draws from the deck & graveyard, meaning it's not restricted to be held either before and/or after poly is drawn.